Andrea - get someone to take some shots of the family, and then either have them blown up to the size you need, or get them "put onto canvas". I know it's not the same as a professional phtographer taking them, but they can still look very effective. My son (10) took one of me and his father, and printed it out on photographic paper on an ordinary pc printer. We framed it, and it hangs in the hall - lovely!
We have photographers take family pics for us every 2 or 3 years, but it is - VERY expensive, done that way.